This research aims to develop and validate a peri-vascular blood volume flowmeter for use in small animal models. Such apparatus will facilitate new research because of its small vessel (0.25 mm o.d.), low flow (4 microL./min.) capabilities. It will furthermore allow the medical researcher to replace multi-animal acute studies with single animal chronic studies in those instances where anesthesia influences organ function. The flowmeter, a scaled down version of apparatus currently manufactured by applicant, will utilize ultrasonic transit-time principles to measure volume flow directly, using non-constrictive flow sensors to minimize alterations of the flow under study. Phase I will address the feasibility of the plans. Prototype miniaturized flow sensors will be constructed and tested in vitro and in vivo and manufacturing technologies evaluated. At two independent universities, chronic and acute research protocols using the prototype flow sensors will be initiated. During Phase II, Phase I design innovations will be incorporated into a prototype flowmeter. The foundation for acceptance of this flowmeter by the scientific community will be laid by continued collaboration with investigators on pilot research projects. Transonic Systems, Inc. will commercialize these technological innovation during Phase III.